Set up an archive and deletion policy for mailboxes in your Office 365 organization

Go to https://protection.office.com
Go to Data governance
Select the Archive.

A list of the mailboxes in your organization is displayed and whether the corresponding archive mailbox is enabled or disabled.
Select all the mailboxes by clicking on the first one in the list, holding down the Shift key, and then clicking the last one in the list.
Under Bulk Edit
Click Enable
Click Yes to close the warning message and start the process to enable the archive mailbox for each selected mailbox.

When the process is complete
Click Refresh to update the list on the Archive page
The archive mailbox is enabled for all user’s in your organization.

Go to Exchange Admin Center
Go to Compliance management
Select retention tags
Create a custom archive policy tag
Click New tag +
Select applied automatically to entire mailbox (default)
Name Type a name for the new retention tag
Retention action Select Move to Archive to move items to the archive mailbox when the retention period expires
Retention period Select When the item reaches the following age (in days), and then enter the duration of the retention period. For this scenario, items will be moved to the archive mailbox after 365 days (1 year)
Comment (Optional) Type a comment that explains the purpose of the custom retention tag
Click Save to create the custom archive tag

Create a custom Deletion policy tag
Click New tag +
Select applied automatically to entire mailbox (default)
Name Type a name for the new retention tag.
Retention action Select Permanently Delete to purge items from the mailbox when the retention period expires.
Retention period Select When the item reaches the following age (in days), and then enter the duration of the retention period. For this scenario, items will be purged after 365 days (1 year)
Comment (Optional) Type a comment that explains the purpose of the custom retention tag.
Click Save to create the custom deletion Tag

In the Exchange Admin Center
Go to Compliance management
Select Retention policies
Click New +
In the Name box, type a name for the new retention policy; for example, Archive and Deletion Policy
Under Retention tags
Click Add New
Select the Custom created retention tags
Click Add
Click OK

In Exchange Admin Center
Go to Recipients
Select Mailboxes

A list of all user mailboxes in your organization is displayed.
Select all the mailboxes by clicking on the first one in the list, holding down the Shift key, and then clicking the last one in the list.
Under Bulk Edit
Click More options
Under Retention Policy
Click Update
Select the retention policy that you created from the drop-down
Click Save

To Verify that the new retention policy was assigned to mailboxes
Select a mailbox on the Mailboxes page
Click Edit
Click Mailbox features

The name of the new policy assigned to the mailbox is displayed in the Retention policy drop-down list.